linux-kernel - Re: [PATCH 0/6] riscv: Relocatable NOMMU kernels

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Message-ID: <60900b42-298c-4b9f-86cf-af31aa5a02d3@sifive.com>
Date: Wed, 26 Feb 2025 09:22:51 -0600
From: Samuel Holland <samuel.holland@...ive.com>
To: Palmer Dabbelt <palmer@...belt.com>
Cc: linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
 akpm@...ux-foundation.org, Arnd Bergmann <arnd@...db.de>,
 alexghiti@...osinc.com
Subject: Re: [PATCH 0/6] riscv: Relocatable NOMMU kernels

Hi Palmer,

On 2025-02-13 8:17 AM, Palmer Dabbelt wrote:
> On Sat, 26 Oct 2024 10:13:52 PDT (-0700), samuel.holland@...ive.com wrote:
>> Currently, RISC-V NOMMU kernels are linked at CONFIG_PAGE_OFFSET, and
>> since they are not relocatable, must be loaded at this address as well.
>> CONFIG_PAGE_OFFSET is not a user-visible Kconfig option, so its value is
>> not obvious, and users must patch the kernel source if they want to load
>> it at a different address.
>>
>> Make NOMMU kernels more portable by making them relocatable by default.
>> This allows a single kernel binary to work when loaded at any address.
>>
>>
>> Samuel Holland (6):
>>   riscv: Remove duplicate CONFIG_PAGE_OFFSET definition
>>   riscv: Allow NOMMU kernels to access all of RAM
>>   riscv: Support CONFIG_RELOCATABLE on NOMMU
>>   asm-generic: Always define Elf_Rel and Elf_Rela
>>   riscv: Support CONFIG_RELOCATABLE on riscv32
>>   riscv: Remove CONFIG_PAGE_OFFSET
>>
>>  arch/riscv/Kconfig               | 10 +---
>>  arch/riscv/Makefile              |  1 -
>>  arch/riscv/include/asm/page.h    | 27 ++++-----
>>  arch/riscv/include/asm/pgtable.h |  6 +-
>>  arch/riscv/mm/init.c             | 97 ++++++++++++++++----------------
>>  include/asm-generic/module.h     |  8 ---
>>  6 files changed, 68 insertions(+), 81 deletions(-)
> 
> I'm getting some build failures
> 
> riscv64-unknown-linux-gnu-ld: arch/riscv/errata/sifive/errata.o: relocation
> R_RISCV_HI20 against `tlb_flush_all_threshold' can not be used when making a
> shared object; recompile with -fPIC
> riscv64-unknown-linux-gnu-ld: arch/riscv/errata/thead/errata.o: relocation
> R_RISCV_HI20 against `riscv_cbom_block_size' can not be used when making a
> shared object; recompile with -fPIC

What toolchain and config do you see failures with? I have tried building this
series on top of v6.14-rc4 with GCC 14.2.1 and
 * defconfig
 * defconfig + NOMMU + S-mode
 * defconfig + NOMMU + M-mode
 * defconfig + 32-bit
 * defconfig + 32-bit + NOMMU + S-mode
 * defconfig + 32-bit + NOMMU + M-Mode
 * nommu_k210_defconfig
 * nommu_k210_sdcard_defconfig
 * nommu_virt_defconfig
and all succeed.

Regards,
Samuel